Constraining the physics of galaxy formation and evolution using galaxy clustering
Watson, Douglas F.
The last decade has transformed the ﬁeld of cosmology into a precision science. We now know to great accuracy that the matter content of the Universe consists of approximately 85% in the form of the mysterious dark matter and the remaining 15% in the form of ordinary, baryonic matter. Much of this baryonic matter is locked up in galaxies, and understanding the spatial distribution, or “clustering”, of galaxies as they relate to the more ubiquitous dark matter is one of the principal goals of galaxy formation theory. There is now an established concordance cosmological model known as ΛCDM. This model has successfully passed a gauntlet of tests on large scales, but studying the small scales (< 1Mpc) is non-trivial, as the physics is quite complicated. This thesis is primarily centered on studying the tumultuous lives of satellite galaxies (galaxies that orbit around a brighter galaxy) by means of the galaxy correlation function, ξ (r), a common statistic that describes the spatial clustering of galaxies. I focus on three distinct, yet connected, unsolved problems of galaxy formation elucidated by galaxy clustering. First, I confront the long-standing conundrum of the observed power-law nature of ξ (r) from a theoretical standpoint. I reveal how a nearly power-law ξ (r) requires a conspiracy between otherwise unrelated physical processes. Second, I discuss a powerful new technique that uses the spatial clustering of satellite galaxies to understand how their stellar mass loss occurs. I ﬁnd the interesting result that low-luminosity satellite galaxies experience substantially more eﬃcient stellar mass loss than luminous satellites. I am also able to successfully predict current intrahalo light (IHL) observations and thus further constrain our stellar mass loss models. Lastly, by modeling recent measurements of the very small-scale clustering of a wide range of galaxy classes, I uncover a strong luminosity trend of the radial density proﬁle of satellite galaxies, wherein bright satellites are poor tracers of the dominant underlying dark matter. This result could possibly lead to a test of the ΛCDM model at the extreme small scales.